Todos to be addressed before the first beta release

[magicant]

We need to address the following issues before the first beta release, which aims to be feature-complete with respect to POSIX 2018.

• Update README
• Failing scripted tests
  • alias-p.sh
    • alias substitution to empty string
    • alias substitution to blank before newline
    • line continuation between alias names (1)
    • Maybe $LINENO not counted correctly with alias? #280
  • command-p.sh
    • command exec retains redirection
  • errexit-p.sh
    • errexit: last of pipeline Support errexit option in multi-command pipelines #362
  • for-p.sh
    • exit status with no words Various fixes #363
  • option-p.sh
    • nounset on: unset variable ${foo+bar} Various fixes #363
    • nounset on: unset variable ${foo:+bar} Various fixes #363
  • param-p.sh
    • length of unset variables, success Various fixes #363
  • path-p.sh
    • expansion with unsearchable directory Various fixes #364
  • quote-p.sh
    • backslashes resulting from expansions (a pattern) Various fixes #364
  • redir-p.sh
    • here-document with non-default file descriptor Various fixes #364
    • multiple here-documents on single command Various fixes #364
  • trap-p.sh
    • fatal shell error in trap Various fixes #364
    • trap command is not affected by redirections effective when set (4) Various fixes #364
• Yash-arith crate
  • None
• Yash-builtin crate
  • None
• Yash-cli crate
  • Disable non-blocking I/O on stdin 071779f
• Yash-env crate
  • Use eaccess 7534090
  • Elaborate catch_signal 33562bd
  • Support real-time signals (2)
  • Variable::expand should require mutable self 528c57d
  • Document VariableRefMut 468ae20
  • Report invalid UTF-8 bytes rather than ignoring them 7e0a45a
  • Make Frame non-exhaustive 3516751
  • Elaborate SelectSystem 57122ee
  • Elaborate AsyncIo 57122ee
  • Elaborate AsyncSignal 57122ee
  • Extend internal handlers for other signals fb1c3a6
• Yash-semantics crate
  • Use /proc/self/exe in fall_back_on_sh f75a019
  • Use pretty::Message and annotate_snippet f1e352f
  • Elaborate Expand for TextUnit (2) 8896664
  • Should we suppress return/break/continue from trap? 905576f
  • Elaborate: Command::execute 8896664
• Yash-syntax crate
  • Consider merging EmptyParam & UnclosedParam into InvalidParamName ccdc4a6
    • We should possibly add InvalidCharInParam to EmptyParam & UnclosedParam.
  • Elaborate the parser::lex::tilde module 68ec273
  • Include the corresponding here-doc operator 34035d1
    • Probably we don't need to do anything.
  • Most FromStr implementations ignore trailing redundant tokens, which should be rejected 93ecc26
  • Elaborate the syntax::pretty module 47cb94a
  • Avoid printing a keyword as the first word 50c2c38